High side transistor switches are often used as switches for automotive components, such as for controlling light sources or other electrically-controlled automotive components. Simple high side switches are often incorporated with additional components to form small sophisticated switch devices with many integrated functions, which may be referred to as Smart Power Switches (or SPS's). A typical SPS may have multiple integrated protection and diagnosis functions. Many embedded device functions require different circuits and sensors. An SPS may incorporate protection functions in the form of a current limitation circuit.
A typical high side switch may have low resistance (i.e., a low-ohmic switch, e.g., of less than 20 milliohms (mOhm)) and may use a double-diffused metal-oxide-semiconductor (DMOS) transistor. For a low-ohmic high side switch, the DMOS transistor typically requires a high charging current for the transistor gate. This is especially true for a high side switch with a fast slew rate (SR), i.e., a high limiting rate of change of the output voltage. Such high slew rates are typically needed for low-ohmic devices and/or higher operating voltages (e.g., a truck operating at greater than 24 volts), where it is desirable to alter the output voltage quickly over a large voltage range. The high side switch is typically designed with a large charge pump circuit to provide a high operating current, to provide the needed high charging current for the transistor gate and to drive the fast switching of output voltage required of the high side switch.